Rename namespace to source-namespace

[sagar-jadhav]

In the current command to copy Secret or ConfigMap, namespace option is used to provide the name of Source Namespace. I think it will be better to rename it to source-namespace similar to target-namespace.

After making the above propose change kube-sync command will look like following:

kube-sync --source-namespace <Source Namespace> --target-namespace <Destination Namespace> secret <Secret Name>

--namespace option can be misunderstood with --namespace option used in kubectl command